Remove duplicate ', ' in dbhash.open()'s argument list.

Doc/lib/libdbhash.tex

@@ -21,7 +21,7 @@ This module provides an exception and a function:
   \exception{KeyError}.  It is a synonym for \exception{bsddb.error}.
 \end{excdesc}
 
-\begin{funcdesc}{open}{path, \optional{, flag\optional{, mode}}}
+\begin{funcdesc}{open}{path\optional{, flag\optional{, mode}}}
   Open a \code{db} database and return the database object.  The
   \var{path} argument is the name of the database file.